It is an iron rule of British politics. Everything Tony did, Gordon has to do better.

Blair went to the Vatican, met the Pope and converted to Catholicism. Brown too has been to the Vatican. He too has met the Pope. But, no, the nation's best known Presbyterian is not - so far as is known - about to embrace popery.

But he has gone one better all the same and had an article published in the Pope's daily. Today's edition of L'Osservatore Romano, which is to the Vatican more or less what Pravda was to the Kremlin, carries a two-column commentary with the byline, "di Gordon Brown".

A footnote explains to the less worldly (or just disbelieving) that the author of the article is indeed the "British prime minister". Today, Brown is due to meet the Pope at the Vatican before lunching with Italy's prime minister, Silvio Berlusconi.

While his contribution to L'Osservatore admittedly took second place on the front page, the prime minister's debut in Vatican journalism appears to have broken new ground. L'Osservatore's editor, Giovanni Maria Vian, said last night he knew of no other instance of a foreign government leader contributing to the paper. "With 148 years of history, it's difficult to be 100% sure," he said. "But it's probable. It's certainly not normal."

The fact that a son of the manse should have been allowed to write where no statesman has written before says much about the unexpectedly close links between Brown and the Holy See. What has brought them together is a common concern for the developing world and what sources close to the prime minister say is his keen appreciation of the Vatican's global influence.

Five years ago, he went to Rome to enlist papal support for his International Finance Facility - a scheme for funding the UN's millennium development goals by selling government backed bonds on international markets. He was back in 2007 to support the Vatican's project underwriting the development of drugs needed in the world's poorer nations.

Their plight in the global economic crisis is the subject of his article today. Brown quotes a World Bank estimate that 2.8 million children under five could die between now and 2015 if the crisis is not checked. "It is as if the entire population of Rome were to die in the next five years," he writes.

The prime minister notes that poor countries also need stimulus packages and adds that he will put before the Group of 20 meeting in London in April a plan for the injection of "billions of dollars into the economies of developing nations".